The invention relates to a procedure and a sheet bar for manufacturing a component out of sheet steel via cold-forming, and to the use of a sheet bar.
During the manufacture of components out of sheet steel, flat sheet bar blanks are usually first manufactured, and then given their final shape in one or more cold-forming steps. In this case, the thickness and properties of the used steel material are determined by the area of the component exposed to the highest loads in practical operation, in particular with respect to larger components fabricated from a single sheet bar.
It has been shown in practice that cold forming sheet steel results in difficulties, for example if the component to be fabricated exhibits a complex shape in view of the deformation processes, or the sheet steel satisfies the requirements placed on its mechanical loading capacity, but is hard to deform due to its material properties. In addition, the thickness required with respect to its loading can complicate the deformation of sheet steel.
For example, when manufacturing curvilinear pipes, it often can be impossible to avoid excessive material thinning in the area of the outer curve of the respective pipe bend, and hence cracks, and also folds on the inner curve of the bend owing to excessive material accumulation. The danger of fold formation during bending can be diminished by using special bending mandrels. In addition, the pipe can be actively pushed during the bending process to influence the reduction in wall thickness in the area of the outer curve to a limited extent However, both measures require a high equipment outlay.
Another example for components with a complex shape that is hard to control with respect to cold forming involves deep drawn cups having a cornered base area. To prevent folds from forming in the area of the corners in such deep drawn parts during deep drawing, braking beads are incorporated on specific points of the deep drawing tool to prevent excessive material flow. At other points where an elevated flow of material is required, the deep drawning tool is lubricated to diminish friction between the material and sheet steel at this location. The outlay associated with these measures is also considerable, and does not yield success for certain materials.
The problems during cold deformation caused by the material properties of the used steel material stem from the fact that materials with a greater thickness or especially high strength must be used to satisfy the requirements placed on the respective component. It is often difficult or even impossible to impart the desired shape to sheet steels made in this way via cold deformation.
According to a procedure known from EF 0 906 799 A1, sheet steel blanks are welded onto a base plate in certain areas on a sheet bar intended for the manufacture of deep drawn body components. The welded-on sheet steel blanks reinforce the sheet bar in such a way that the component manufactured out of the sheet bar reliably satisfies the mechanical requirements placed on this part. To ensure that the welded-on sheet steel blanks also have a sufficient deformability, material accumulations are formed on the surface of the sheet steel blanks.
The procedure known from EP 0 906 799 A1 does make it possible to manufacture components having a high mechanical loading capacity at a diminished weight. However, practice has shown that it is hard to deform sheet bars reinforced in this way, despite the special design of the reinforcement sheet steel. This holds true in particular if the base plate onto which the reinforcement sheet steel is welded exhibits poor forming properties.
Proceeding from the prior art described above, the object of the invention is to provide a procedure that ensures an improved result of cold forming, or even enables the manufacture of specific component shapes in the first place. In addition, sheet bars with an improved formability are to be provided. Finally, advantageous uses for such sheet bars are to be specified.